Chapter 2: Traps Revisited
The rules for traps in the Dungeon Master’s Guide provide the basic information you need to manage traps at the game table. The material here takes a different, more elaborate approach — describing traps in terms of their game mechanics and offering guidance on creating traps of your own using these new rules.
Rather than characterize traps as mechanical or magical, these rules separate traps into two other categories: simple and complex.
A simple trap activates and is thereafter harmless or easily avoided. A hidden pit dug at the entrance of a goblin lair, a poison needle that pops from a lock, and a crossbow rigged to fire when an intruder steps on a pressure plate are all simple traps.
Elements of a Simple Trap
The description of a simple trap begins with a line that gives the trap’s level and the severity of the threat it poses. Following a general note on what the trap looks like and how it functions are three paragraphs that tell how the trap works in the game.
Level and Threat. A trap’s level is actually a range of levels, equivalent to one of the tiers of play (levels 1–4, 5–10, 11–16, and 17–20), indicating the appropriate time to use the trap in your campaign. Additionally, each trap poses either a moderate, dangerous, or deadly threat, based on its particular details.
Trigger. A simple trap activates when an event occurs that triggers it. This entry in a trap’s description gives the location of the trigger and the activity that causes the trap to activate.
Effect. A trap’s effect occurs after it activates. The trap might fire a dart, unleash a cloud of poison gas, cause a hidden enclosure to open, and so on. This entry specifies what the trap targets, its attack bonus or saving throw DC, and what happens on a hit or a failed saving throw.
Countermeasures. Traps can be detected or defeated in a variety of ways by using ability checks or magic. This entry in a trap’s description gives the means for counteracting the trap. It also specifies what happens, if anything, on a failed attempt to disable it.
MAKING TRAPS MEANINGFUL
If you want to improve the chance that the characters will come up against the traps you’ve set for them in an encounter or an adventure, it can be tempting to use a large number of traps. Doing so ensures that the characters will have to deal with at least one or two of them, but it’s better to fight that urge.
If your encounters or adventures are sown with too many traps, and if the characters are victimized over and over again as a result, they are likely to take steps to prevent further bad things from happening. Because of their recent experience, the characters can become overly cautious, and you run the risk of the action grinding to a halt as the players search every square inch of the dungeon for trip wires and pressure plates.
Traps are most effective when their presence comes as a surprise, not when they appear so often that the characters spend all their effort watching out for the next one.
Running a Simple Trap
To prepare for using a simple trap in play, start by making note of the characters’ passive Wisdom (Perception) scores. Most traps allow Wisdom (Perception) checks to detect their triggers or other elements that can tip off their presence. If you stop to ask players for this information, they might suspect a hidden danger.
When a trap is triggered, apply its effects as specified in its description.
If the characters discover a trap, be open to adjudicating their ideas for defeating it. The trap’s description is a starting point for countermeasures, rather than a complete definition.
To make it easier for you to describe what happens next, the players should be specific about how they want to defeat the trap. Simply stating the desire to make a check isn’t helpful for you. Ask the players where their characters are positioned and what they intend to do to defeat the trap.
Example Simple Traps
Simple trap (level 1–4, dangerous threat)
A bear trap resembles a set of iron jaws that springs shut when stepped on, clamping down on a creature’s leg. The trap is spiked in the ground, leaving the victim immobilized.
Trigger. A creature that steps on the bear trap triggers it.
Effect. The trap makes an attack against the triggering creature. The attack has a +8 attack bonus and deals 5 (1d10) piercing damage on a hit. This attack can’t gain advantage or disadvantage. A creature hit by the trap has its speed reduced to 0. It can’t move until it breaks free of the trap, which requires a successful DC 15 Strength check by the creature or another creature adjacent to the trap.
Countermeasures. A successful DC 10 Wisdom (Perception) check reveals the trap. A successful DC 10 Dexterity check using thieves’ tools disables it.
Simple trap (level 1–4, dangerous threat)
The crossbow trap is a favorite of kobolds and other creatures that rely on traps to defend their lairs. It consists of a trip wire strung across a hallway and connected to a pair of hidden heavy crossbows. The crossbows are aimed to fire down the hallway at anyone who disturbs the trip wire.
Trigger. A creature that walks through the trip wire triggers the trap.
Effect. The trap makes two attacks against the triggering creature. Each attack has a +8 attack bonus and deals 5 (1d10) piercing damage on a hit. This attack can’t gain advantage or disadvantage.
Countermeasures. A successful DC 15 Wisdom (Perception) check reveals the trip wire. A successful DC 15 Dexterity check using thieves’ tools disables the trip wire, and a check with a total of 5 or lower triggers the trap.
Simple trap (level 1–4, moderate threat)
Some folk who build dungeons, such as mad wizards in search of new victims, have no intention of allowing their visitors to make an easy escape. A falling portcullis trap can be especially devious if it causes a portcullis to drop some distance away from the pressure plate that activates the trap. Although the trap is deep in the dungeon, the portcullis closes off the dungeon entrance, which is hundreds of feet away, meaning that adventurers don’t know they are trapped until they decide to head for the exit.
Trigger. A creature that steps on the pressure plate triggers the trap.
Effect. An iron portcullis drops from the ceiling, blocking an exit or a passageway.
Countermeasures. A successful DC 20 Wisdom (Perception) check reveals the pressure plate. A successful DC 20 Dexterity check using thieves’ tools disables it, and a check with a total of 5 or lower triggers the trap.
Simple trap (level 5–10, dangerous threat)
The temple of Pyremius, a god of fire, is threatened by thieves who seek to steal the fire opals displayed there by the priests in tribute to their god. A mosaic on the floor of the entryway to the inner sanctum delivers a fiery rebuke to intruders.
Trigger. Anyone who steps on the mosaic causes fire to erupt from it. Those who openly wear holy symbols of Pyremius don’t trigger this trap.
Effect. A 15-foot cube of fire erupts, covering the pressure plate and the area around it. Each creature in the area must make a DC 15 Dexterity saving throw, taking 24 (7d6) fire damage on a failed save, or half as much damage on a successful one.
Countermeasures. A successful DC 15 Wisdom (Perception) check reveals the presence of ash and faint burn marks in the area affected by this trap. A successful DC 15 Intelligence (Religion) check enables a creature to destroy the trap by defacing a key rune on the perimeter of the mosaic that is within reach; failing this check causes the trap to activate. A successful dispel magic (DC 15) cast on the runes destroys the trap.
Simple trap (level 1–4, dangerous threat)
Goblins, with their propensity to enslave their enemies, prefer traps that leave intruders intact so the victims can be put to work in the mines or elsewhere.
Trigger. A trip wire strung across a hallway is rigged to a large net. If the trip wire is broken, the net falls on intruders. An iron bell is also rigged to the trip wire. It rings when the trap activates, alerting nearby guards.
Effect. A net covering a 10-foot-by-10-foot area centered on the trip wire falls to the floor as a bell rings. Any creature fully within this area must succeed on a DC 15 Dexterity saving throw or be restrained. A creature can use its action to make a DC 10 Strength check to try to free itself or another creature in the net. Dealing 5 slashing damage to the net (AC 10, 20 hp) also frees a creature without harming the creature.
Countermeasures. A successful DC 15 Wisdom (Perception) check reveals the trip wire and the net. A successful DC 15 Dexterity check using thieves’ tools disables the trip wire without causing the net to drop or the bell to ring; failing the check causes the trap to activate.
The simplest of pit traps consists of a 10-foot-deep hole in the floor, concealed by tattered canvas that’s covered with leaves and dirt to look like solid ground. This type of trap is useful for blocking off the entrance to a monster lair, and usually has narrow ledges along its sides to allow for movement around it.
Trigger. Anyone who steps on the canvas might fall into the pit.
Effect. The triggering creature must make a DC 10 Dexterity saving throw. On a successful save, the creature catches itself on the pit’s edge or instinctively steps back. On a failed save, the creature falls into the pit and takes 3 (1d6) bludgeoning damage from the fall.
Countermeasures. A successful DC 10 Wisdom (Perception) check reveals the presence of the canvas and the 1-foot-wide ledge around the edges of the pit where it is safe to travel.
Pit traps are hilarious!
Because when one of you walking
things steps on one, you fall down!
And you get hurt! That’s the best part.
Simple trap (level 1–4, deadly threat)
A tiny, poisoned needle hidden in a lock is a good way to discourage thieves from plundering a hoard. Such a trap is usually put in a chest or in the door to a treasure chamber.
Trigger. Anyone attempting to pick or open the lock triggers the trap.
Effect. The triggering creature must make a DC 20 Constitution saving throw. On a failed save, the creature takes 14 (4d6) poison damage and is poisoned for 10 minutes. While poisoned in this way, the creature is paralyzed. On a successful save, the creature takes half as much damage and isn’t poisoned.
Countermeasures. A successful DC 20 Wisdom (Perception) check reveals the needle, but only if a character inspects the lock. A successful DC 20 Dexterity check using thieves’ tools disables the needle, and a check with a total of 10 or lower triggers the trap.
Simple trap (level 5–10, dangerous threat)
This trap uses moving blades that sweep down through a chamber, threatening anyone nearby. Typically, a scything blade trap is activated by manipulating a lever or some other simple device. Kobolds especially like this kind of trap, since it can take down bigger creatures.
Trigger. When the lever is pulled, the trap activates.
Effect. Each Medium or larger creature in a 5-foot-wide, 20-foot-long area must make a DC 15 Dexterity saving throw, taking 14 (4d6) slashing damage on a failed save, or half as much damage on a successful one.
Countermeasures. The lever isn’t hidden. A successful DC 15 Wisdom (Perception) check involving the surfaces in the trap’s area of effect reveals scrape marks and bloodstains on the walls and floor. A successful DC 15 Dexterity check using thieves’ tools disables the lever.
Sleep of Ages
Simple trap (level 11–16, deadly threat)
When a sleep of ages trap activates, a pressure plate unleashes a spell that threatens to send intruders into a deep slumber. The dungeon’s guardians can then more easily dispose of the sleepers.
Trigger. Stepping on the pressure plate triggers this trap.
Effect. When activated, this trap casts a sleep spell centered on the pressure plate, using a 9th-level spell slot.
Countermeasures. A successful DC 20 Wisdom (Perception) check reveals the pressure plate. A successful DC 20 Intelligence (Arcana) check made within 5 feet of the pressure plate disables the trap, and a check with a total of 10 or lower triggers it. A successful dispel magic (DC 19) cast on the pressure plate destroys the trap.
Designing Simple Traps
You can create your own simple traps by using the following guidelines. You can also adapt the example traps for different levels and severity of threat by modifying their DCs and damage values as shown below.
Before diving into the details of your trap, think about its reason for being. Why would someone build such a trap? What is its purpose? Consider the trap’s creator (in the adventure), the creator’s purpose, and the location the trap protects. Traps have context in the world — they aren’t created for no reason — and that context drives the trap’s nature and effects.
Described below are a few of the general purposes a trap might have. Use them to inspire the creation of your own traps.
Alarm. An alarm trap is designed to alert an area’s occupants of intruders. It might cause a bell or a gong to sound. This type of trap rarely involves a saving throw, because the alarm can’t be avoided when the trap goes off.
Delay. Some traps are designed to slow down enemies, giving a dungeon’s inhabitants time to mount a defense or flee. The hidden pit is a classic example of this kind of trap. A 10-foot-deep pit usually deals little damage and is easy to escape, but it serves its purpose by impeding intruders. Other examples of delaying traps include collapsing walls, a portcullis that drops from the ceiling, and a locking mechanism that shuts and bars a door. If a delaying trap has moving parts that directly threaten characters when they operate, the characters are usually required to make Dexterity saving throws to avoid harm.
Restrain. A restraining trap tries to keep its victims in place, leaving them unable to move. Such traps are often employed in conjunction with regular guard patrols, so that victims are periodically extricated and taken away to be dealt with. But in an ancient dungeon, the guards might be long gone.
Restraining traps usually require a successful Strength saving throw to be avoided, but some don’t allow saving throws. In addition to dealing damage, a restraining trap also renders a creature unable to move. Making a subsequent successful Strength check (using the trap’s saving throw DC) or dealing damage against the trap can break it and free the captive. Examples include a bear trap, a cage that drops from a ceiling, and a device that flings a net.
Slay. Some traps are designed to eliminate intruders, plain and simple. Their effects include poisoned needles that spring out when a lock is tampered with, blasts of fire that fill a room, poison gas, and other lethal measures. Saving throws — usually Dexterity or Constitution — allow creatures to avoid or mitigate the trap’s effects.
Level and Lethality
Before creating a trap’s effects, think about its level and its lethality.
Traps are divided into four level ranges: 1–4, 5–10, 11–16, and 17–20. The level you choose for a trap gives you a starting point for determining its potency.
To further delineate the trap’s strength, decide whether it is a moderate, dangerous, or deadly threat to characters in its level range. A moderate trap is unlikely to kill a character. A dangerous trap typically deals enough damage that a character hit by one is eager for healing. A deadly trap might reduce a creature to 0 hit points in one shot, and leaves most creatures hit by it in need of a short or long rest.
Consult the following tables when determining a trap’s effects. The Trap Save DCs and Attack Bonuses table provides guidelines for a trap’s saving throw DC, check DC, and attack bonus. The check DC is the default for any check used to interact with the trap.
The Damage Severity by Level table lists the typical damage a trap deals at certain character levels. The damage values given assume that the trap damages one creature. Use d6s for damage in place of d10s for traps that can affect more than one creature at a time.
The Spell Equivalent by Level table shows the spell slot level that is appropriate for a given character level and the severity of danger posed by the trap. A spell is a great foundation to use as the design of a trap, whether the trap duplicates the spell (a mirror that casts charm person on whoever looks into it) or uses its effects (an alchemical device that explodes like a fireball).
The Deadly entry for characters of 17th level or higher suggests combining a 9th-level and a 5th-level spell into one effect. In this case, pick two spells, or combine the effects of a spell cast using a 9th-level and a 5th-level slot. For instance, a fireball spell of this sort would deal 24d6 fire damage on a failed saving throw.
Trap Save DCs and Attack Bonuses
|Trap Danger||Save/Check DC||Attack Bonus|
Damage Severity by Level
|1-4||5 (1d10)||11 (2d10)||22 (4d10)|
|5-10||11 (2d10)||22 (4d10)||55 (10d10)|
|11-16||22 (4d10)||55 (10d10)||99 (18d10)|
|17-20||55 (10d10)||99 (18d10)||132 (24d10)|
Spell Equivalent by Level
|17-20||6th||9th||9th + 5th|
A trigger is the circumstance that needs to take place to activate the trap.
Decide what causes the trap to activate and determine how the characters can find the trigger. Here are some example triggers:
- A pressure plate that, when it is stepped on, activates the trap
- A trip wire that springs a trap when it is broken, usually when someone walks through it
- A doorknob that activates a trap when it is turned the wrong way
- A door or chest that triggers a trap when it is opened
A trigger usually needs to be hidden to be effective. Otherwise, avoiding the trap is usually easy.
A trigger requires a Wisdom (Perception) check if simply spotting it reveals its nature. The characters can foil a pit trap hidden by a leaf-covered net if they spot the pit through a gap in the leaves. A trip wire is foiled if it is spotted, as is a pressure plate.
Other traps require careful inspection and deduction to notice. A doorknob opens a door when turned to the left, but activates a trap when turned to the right. Such a subtle trap requires a successful Intelligence (Investigation) check to notice. The trigger is obvious. Understanding its nature is not.
The DC of the check, regardless of its type, depends on the skill and care taken to conceal the trap. Most traps can be detected with a successful DC 20 check, but a crudely made or hastily built trap has a DC of 15. Exceptionally devious traps might have a DC of 25.
You must then put some thought into what the characters learn with a successful check. In most cases, the check reveals the trap. In other cases, it uncovers clues, but foiling the trap still requires some deduction. The characters might succeed on the check but still trigger the trap if they don’t understand what they have learned.
Designing a trap’s effects is a straightforward process. The tables for saving throw DCs, attack bonuses, damage, and the like give you a starting point for most simple traps that deal damage.
For traps with more complex effects, your best starting point is to use the Spell Equivalent by Level table to find the best match for your trap’s intended effect. Spells are a good starting point because they are compact pieces of game design that deliver specific effects.
If you are using a spell as a starting point, check to see if you need to tweak its effects to fit the trap’s nature. For instance, you can easily change the damage type a spell delivers or the saving throw it requires.
Disarming a Simple Trap
Only one successful ability check is required to disarm a simple trap. Imagine how your trap operates, and then think about how the characters could overcome it. More than one kind of ability check might be possible. Some traps are so poorly concealed that they can be discovered or circumvented without active effort. For instance, a hidden pit trap is effectively disarmed as soon as the characters notice it. After that, they can simply walk around it, or they can climb down one side, walk across the bottom of the pit, and climb up the other side.
Once you determine how a trap can be disarmed or avoided, decide the appropriate ability and skill combinations that characters can use. A Dexterity check using thieves’ tools, a Strength (Athletics) check, and an Intelligence (Arcana) check are all commonly used for this purpose.
A Dexterity check using thieves’ tools can apply to any trap that has a mechanical element. Thieves’ tools can be used to disable a trip wire or a pressure plate, disassemble a poison needle mechanism, or clog a valve that leaks poisonous gas into a room.
A Strength check is often the method for thwarting traps that can be destroyed or prevented from operating through the use of brute force. A scything blade can be broken, a sliding block can be held in place, or a net can be torn apart.
A magic trap can be disabled by someone who can undermine the magic used to power it. Typically, a successful Intelligence (Arcana) check enables a character to figure out how a magic trap functions and how to negate its effect. For instance, the character could discover that a statue that belches a jet of magical flame can be disabled by shattering one of its glass eyes.
Once you know what kind of check is called for, you then determine what happens on a failed attempt to disable the trap. Depending on the kind of check involved and the nature of the trap, you might determine that any failed check has negative consequences — usually involving the triggering of the trap. At other times, you could assign a number that the check must exceed to prevent the trap from going off. If the total of the check is equal to or lower than that number, the trap activates.
Placing a Simple Trap
Context and environment are critical when it comes to properly locating a trap. A swinging log trap that’s meant to knock characters aside is a mere inconvenience on a typical forest path, where it can be easily circumvented. But it’s a potentially deadly hazard on a narrow trail that hugs the side of a towering cliff face.
Choke points and narrow passages that lead to important places in a dungeon are good spots for traps, especially those that serve as alarms or restraints. The goal is to foil or delay intruders before they can reach a critical location, giving the dungeon’s denizens a chance to mount a defense or a counterattack.
A treasure chest, a door leading to a vault, or any other obstacle or container that bars the way to a valuable treasure is the ideal location for a slaying trap. In such instances, the trap is the last line of defense against a thief or intruder.
Alarm traps, since they pose no direct physical threat, are appropriate for areas that are also used by a dungeon’s denizens — assuming the residents know about the trap and how to avoid setting it off. Accidents can happen, but if a goblin stumbles inside its den and activates an alarm trap, there’s no real harm done. The alarm sounds, the guards arrive, they punish the clumsy goblin, and they reset the trap.
A complex trap poses multiple dangers to adventurers. After a complex trap activates, it remains dangerous round after round until the characters avoid it or disable it. Some complex traps become more dangerous over time, as they accumulate power or gain speed.
Complex traps are also more difficult to disable than simple ones. A single check is not enough. Instead, a series of checks is required to slowly disengage the trap’s components. The trap’s effect degrades with each successful check until the characters finally deactivate it.
Most complex traps are designed so that they can be disarmed only by someone who is exposed to the trap’s effect. For example, the mechanism that controls a hallway filled with scything blades is on the opposite end from the entrance, or a statue that bathes an area in necrotic energy can be disabled only by someone standing in the affected area.
Describing a Complex Trap
A complex trap has all the elements of a simple trap, plus special characteristics that make the trap a more dynamic threat.
Level and Threat. A complex trap uses the same level and severity designations that a simple trap does.
Trigger. Just like a simple trap, a complex trap has a trigger. Some complex traps have multiple triggers.
Initiative. A complex trap takes turns as a creature does, because it functions over a period of time. This part of a trap’s description tells whether the trap is slow (acts on initiative count 10), fast (acts on initiative count 20), or very fast (acts on initiative count 20 and also initiative count 10). A trap always acts after creatures that have the same initiative count.
Active Elements. On a trap’s turn, it produces specific effects that are detailed in this part of its description. The trap might have multiple active elements, a table you roll on to determine its effect at random, or options for you to choose from.
Dynamic Elements. A dynamic element is a threat that arises or evolves while the trap functions. Usually, changes involving dramatic elements take effect at the end of each of the trap’s turns or in response to the characters’ actions.
Constant Elements. A complex trap poses a threat even when it is not taking its turn. The constant elements describe how these parts of the trap function. Most make an attack or force a saving throw against any creature that ends its turn within a certain area.
Countermeasures. A trap can be defeated in a variety of ways. A trap’s description details the checks or spells that can detect or disable it. It also specifies what happens, if anything, on a failed attempt to disable it.
Disabling a complex trap is like disarming a simple trap, except that a complex trap requires more checks. It typically takes three successful checks to disable one of a complex trap’s elements. Many of these traps have multiple elements, requiring a lot of work to shut down every part of the trap. Usually, a successful check reduces a trap element’s effectiveness even if it doesn’t disable the trap.
Running a Complex Trap
A complex trap functions in play much like a legendary monster. When it is activated, the trap’s active elements act according to its initiative. On each of its initiative counts, after all creatures with that same initiative count have acted, the trap’s features activate. Apply the effects detailed in the trap’s description.
After resolving the effects of the trap’s active elements, check its dynamic elements to see if anything changes about the trap. Many complex traps have effects that vary during an encounter. A magical aura might do more damage the longer it is active, or a swinging blade might change which area of a chamber it attacks.
The trap’s constant elements allow it to have effects when it isn’t the trap’s turn. At the end of each creature’s turn, look at the trap’s constant elements to see if any of their effects are triggered.
Experience for Complex Traps
Overcoming a complex trap merits an experience point award, depending on the danger it poses. Judging whether a party has overcome a trap requires some amount of adjudication. As a rule of thumb, if the characters disable a complex trap or are exposed to its effects and survive, award them experience points for the effort according to the table below.
Complex Trap Experience Awards
|Trap Level||Experience Points|
Example Complex Traps
The following complex traps can be used to challenge characters or to inspire your own creations.
Path of Blades
Complex trap (level 1–4, dangerous threat)
Hidden within a buried pyramid that marks the location of the Lost City of Cynidicea is the tomb of King Alexander and Queen Zenobia. The entrance to their tomb is a long hallway riddled with traps, accessible only by cunningly hidden secret doors. The hallway is 20 feet wide and 160 feet long. It is mostly clear. After 80 feet, the floor is broken and cracked, becoming difficult terrain until the 130-foot mark.
Trigger. This trap activates as soon as a non-undead creature enters the hallway, and it remains active while any non-undead creature is within the hall.
Initiative. The trap acts on initiative count 20 and initiative count 10.
Active Elements. The Path of Blades includes a set of whirling blades along the first 80 feet of the trap, crushing pillars that slam down from the ceiling to the floor before rising back up to the ceiling in the next 50 feet, and a rune of fear in its final 30 feet.
Whirling Blades (Initiative 20). The blades attack each creature in the first 80 feet of the hallway, with a +5 bonus to the attack roll and dealing 11 (2d10) slashing damage on a hit.
Crushing Pillars (Initiative 10). Each creature in the 50-foot-long area beyond the first 80 feet of the hallway must make a DC 15 Dexterity saving throw. On a failed save, a creature takes 11 (2d10) bludgeoning damage and is knocked prone. On a successful save, the creature takes half as much damage and isn’t knocked prone.
Rune of Fear (Initiative 10). Each creature in the 30-foot-long area beyond the Crushing Pillars must make a DC 15 Wisdom saving throw. On a failed saving throw, the creature becomes frightened by the rune, and it must immediately use its reaction to move its speed in the direction of the pillars. The frightened creature can’t move closer to the far end of the hallway until it uses its action to make a DC 15 Wisdom saving throw, which ends the frightened condition on itself on a success.
Dynamic Elements. The blades and the rune become more dangerous the longer the trap remains active.
Blades Accelerate. The blades move with increasing speed, slowing only when they hit a target. Each time the blades miss with an attack, their next attack becomes harder to avoid. After each miss, the blades’ attack bonus increases by 2, and their damage increases by 3 (1d6). These benefits apply until the blades hit a target, after which the values return to normal.
Rune’s Defense. Tampering with the Rune of Fear increases the trap’s power. Each successful check on an attempt to disable the rune increases the damage of the blades and the crushing pillars by 5 (1d10) and increases the rune’s saving throw DC by 1.
Constant Elements. The Whirling Blades and the Rune of Fear affect each creature that ends its turn in an area affected by these elements.
Whirling Blades. Any creature that ends its turn in the blades’ area is targeted by an attack: +5 attack bonus; 5 (1d10) slashing damage on a hit.
Rune of Fear. Any creature that ends its turn within 30 feet of the far end of the corridor must make a saving throw against the Rune of Fear effect.
Countermeasures. Each of the trap’s active elements can be thwarted by particular countermeasures.
Whirling Blades. Characters can smash the blades, damage their components, or discern how to avoid them. The blades are disabled if their attack bonus is reduced to −8. Ways to reduce it are described below.
Intelligence (Investigation), DC 15. As an action, a creature that can see the blades can attempt an Intelligence (Investigation) check. A successful check means that the character has learned how to anticipate the blades’ movement, imposing disadvantage on the blades’ attacks against the creature while it isn’t incapacitated.
Attack. A creature in the area can ready an attack to strike at one of the blades as it goes by. The blade gains advantage on its attack against the creature. The creature then attacks. Each blade has AC 15 and 15 hit points. Destroying a blade reduces the Whirling Blades attack bonus by 2.
Dexterity check using thieves’ tools, DC 15. Creatures can use thieves’ tools in the area attacked by the blades to foil their mechanism. A successful check reduces the Whirling Blades attack bonus by 2.
Crushing Pillars. The pillars are not susceptible to countermeasures.
Rune of Fear. The rune can be disabled with three successful DC 15 Intelligence (Arcana) checks. Each check requires an action. A creature must be at the end of the hallway to attempt the check, and only one creature can work on this task at once. Once a creature attempts a check for this purpose, no other character can do so until the end of that creature’s next turn. Alternatively, the rune can be disabled with three successful castings of dispel magic (DC 13) targeting the rune.
Sphere of Crushing Doom
Complex trap (level 5–10, deadly threat)
The court jester devised a deadly trap to foil anyone who sought to steal his magic fool’s cap. The jester’s tomb is located at the end of a 10-foot-wide, 150-foot-long hallway that descends sharply from north to south. The entrance to the tomb is a door on the eastern wall at the bottom of the slope, at the south end of the hall.
Trigger. This trap activates as soon as the door leading to the jester’s coffin is opened. A magic portal opens at the northern end of the hallway and disgorges an enormous steel sphere, which hurtles down the slope. When it reaches the bottom of the slope, a second portal briefly appears and teleports the sphere back to the top of the slope to begin the process again.
Initiative. The trap acts on initiative count 10 (but see the dynamic element below).
Active Element. Although the trap is complex in nature, it has a single active element. That’s all it needs.
Sphere of Crushing Doom (Initiative 10). The trap’s active element is a sphere of steel that almost fills the 10-foot width of the hallway and rolls to the bottom of the slope on its turn. Each creature in the sphere’s path must make a DC 20 Strength saving throw. On a failed save, a creature takes 22 (4d10) bludgeoning damage and is knocked prone. On a successful save, a creature takes half as much damage and isn’t knocked prone. Objects that block the sphere, such as a conjured wall, take maximum damage from the impact.
Dynamic Element. The longer it rolls, the more lethal the sphere becomes.
Speed Kills. After its turn, the sphere gains speed, represented by its damage increasing by 11 (2d10). While its damage is 55 (10d10) or greater, it acts on initiative count 20 and 10.
Countermeasures. The trap can be neutralized either by stopping the sphere or preventing it from teleporting.
Stop the Sphere. Stopping the sphere is the easiest way to disrupt the trap. A wall of force can do so easily, as can any object placed in its path that has enough hit points to absorb damage from the sphere without being destroyed.
Disrupt the Portals. Either portal can be neutralized with three successful DC 20 Intelligence (Arcana) checks, but the process of analyzing a portal to disrupt it takes time. Faint runes in the ceiling and floor at both ends of the hallway are involved in the functioning of the portals. A creature must first use an action to examine a set of runes, then use a subsequent action to attempt to vandalize the runes. Each successful check reduces the sphere’s damage by 11 (2d10), as the disrupted sphere loses speed moving through the failing portal.
Alternatively, a set of runes can be disabled with three successful castings of dispel magic (DC 19) targeting any of the runes in the set.
If the southern portal is destroyed, the sphere slams into the south wall and comes to a halt. It blocks the door to the tomb, but the characters can escape.
Complex trap (level 11–16, deadly threat)
This fiendish trap was built to eliminate intruders who infiltrate a yuan-ti temple. The trap is a room, 60 feet on a side, with 5-foot-wide stone doors in the middle of each wall. In each corner of the room stands a 10-foot-tall statue of a great serpent, coiled and ready to strike. The eyes in each statue are rubies worth 200 gp apiece.
Trigger. This trap activates when a ruby is pried from one of the statues. Each statue’s mouth slides open, revealing a 1-foot-wide pipe that runs down its throat.
Initiative. The trap acts on initiative count 20 and initiative count 10.
Active Elements. The trap fills the room with poison and other deadly effects.
Locked Doors (Initiative 20). The four doors to this room slam shut and are locked in place by magic. This effect activates only once, the first time the trap is triggered.
Poison Gas (Initiative 20). Poison gas floods the room. Each creature inside must make a DC 20 Constitution saving throw, taking 33 (6d10) poison damage on a failed save, or half as much damage on a successful one.
Tempest (Initiative 10). Air and gas boils from the trap. Roll a d6, and consult the following table.
|1||Hallucinatory gas scrambles the mind and senses. All Intelligence and Wisdom checks made in the room have disadvantage until the Tempest element activates again.|
|2||Explosive gas fills the area. If anyone holds an open flame, it causes an explosion. All creatures in the area must make a DC 20 Dexterity saving throw, taking 22 (4d10) fire damage on a failed save, or half as much damage on a successful one. The flame is then extinguished.|
|3||Weakening gas fills the room. All Strength and Dexterity checks made in the room have disadvantage until the Tempest element activates again.|
|4||Buffeting winds force each creature in the room to succeed on a DC 20 Strength saving throw or be knocked prone.|
|5||Smoke fills the room. Visibility is reduced to 1 foot until the next time the Tempest element activates.|
|6||Poison floods the room, forcing creatures to make saving throws as for the Poison Gas element.|
Dynamic Element. The longer the poison gas remains in the room, the more lethal it becomes.
Increased Potency. The damage from the Poison Gas element increases by 11 (2d10) each round after it activates, to a maximum of 55 (10d10).
Countermeasures. There are a few ways that the trap can be overcome.
Open the Doors. Opening the doors is the quickest way to circumvent the trap, but they are warded with magic. To open the doors, a character must first succeed on a DC 20 Wisdom (Perception) check to find the locking mechanism. A successful DC 20 Intelligence (Arcana) check is then required to disable the sphere of force that surrounds the lock (dispel magic is ineffective against it). Success on a DC 20 Dexterity check using thieves’ tools picks the lock. Finally, a successful DC 20 Strength (Athletics) check is needed to push the door open. Each check requires an action.
Disable the Statues. A statue can be disabled by blocking the flow of gas from its mouth. Heavily damaging a statue is a bad idea, for doing so leaves the gas vents open. Reducing a statue to 0 hit points (AC 17; 20 hp; resistance to fire, piercing, and slashing damage; immune to poison and psychic damage) or making a successful DC 20 Strength check to break it cracks the statue and increases the Poison Gas damage by 5 (1d10). A successful DC 20 Dexterity check using thieves’ tools, or a successful DC 15 Strength check made to block up the statue with a cloak or similar object, decreases the poison damage by 5 (1d10). Once a character succeeds on the check, someone must remain next to the statue to keep it blocked up. When all four statues are blocked in this manner, the trap deactivates.
Designing Complex Traps
Creating a complex trap takes more work than building a simple one, but with some practice, you can learn the process and make it move quickly.
Familiarize yourself with the advice on designing a simple trap before proceeding with the guidelines on complex traps.
Complex traps are typically designed to protect an area by killing or disabling intruders. It is worth your time to consider who made the trap, the trap’s purpose, and its desired result. Does the trap protect a treasure? Does it target only certain kinds of intruders?
Level and Lethality
Complex traps use the same level designations and lethality descriptors that simple traps do. Refer to that section for a discussion of how level and lethality help determine saving throw and check DCs, attack bonuses, and other numerical elements of a complex trap.
A complex trap has multiple parts, typically relies on the characters’ positions to resolve some of its effects, and can bring several effects to bear in each round. The traps are called complex for a reason! To begin the design process, consider drawing a map of the area to be affected by the trap on graph paper, using a scale of 5 feet per square. This level of detail allows you to develop a clear idea of what the trap can do and how each of its parts interact. Your map is the starting point and context for the rest of the design process.
Don’t limit yourself to one room. Look at the passages and rooms around the area of the trap and think about the role they can play. The trap might cause doors to lock and barriers to fall into place to prevent escape. It could cause darts to fire from the walls in one area, forcing characters to enter rooms where other devices trigger and threaten them.
Consider how terrain and furniture can add to the trap’s danger. A chasm or a pit might create a buffer that allows a trap to send bolts of magic at the characters, while making it difficult or even impossible for them to reach the runes they must deface to foil that attack.
Think of your map like a script. Where do the characters want to go? What does the trap protect? How can the characters get there? What are their likely escape routes? Answering these questions tells you where the trap’s various elements should be placed.
A complex trap’s active elements work the same way as a simple trap’s effects, except that a complex trap activates in every round. Otherwise, the guidelines for picking saving throw DCs, attack bonuses, and damage are the same. To make your trap logically consistent, make sure the elements you design can activate each round. For instance, ordinary crossbows rigged to fire at the characters would need a mechanism for reloading them between attacks.
In terms of lethality, it’s better to have multiple dangerous effects in a trap than a single deadly one. For example, the Path of Blades trap uses two dangerous elements and one moderate element.
It’s useful to create multiple active elements, with each affecting a different area. It’s also a good idea to use a variety of effects. Some parts of the trap might deal damage, and others might immobilize characters or isolate them from the rest of the party. A bashing lever might knock characters into an area engulfed by jets of flame. Think about how the elements can work together.
In addition to the active steps a complex trap takes, it should also present a continual hazard. Often, the active and constant effects are the same thing. Imagine a hallway filled with whirling saw blades. On the trap’s turn, the blades attack anyone in the hall. In addition, anyone who lingers in the hallway takes damage at the end of each of their turns, accounting for the constant threat that the blades pose.
A constant element should apply its effect to any creature that ends its turn in that element’s area. If an active element presents a threat when it isn’t the trap’s turn, define the threat it poses as a constant element. As a rule of thumb, keep the saving throw DC or attack bonus the same as for the active element but reduce the damage by half.
Avoid filling the entire encounter area with constant elements. Part of the challenge of a complex trap lies in figuring out which areas are safe. A moment’s respite can help add an element of pacing to an encounter with a complex trap and give the characters the feeling that they aren’t in constant peril. For example, walls that slam together might need to reset between slams, making them harmless when it isn’t their turn to act.
Just as a battle is more interesting if the monsters change their tactics or unveil new abilities in later rounds, so too are complex traps more fun if their nature changes in some way. The whirling blades that protect a treasure chest do more damage each round as they speed up. The poison gas in a room grows thicker as more of it floods the chamber, dealing greater damage and affecting line of sight. The necrotic aura around an idol of Demogorgon produces random effects each time its active element is triggered. As water floods a chamber, the characters must swim across areas they could walk through just a round or two earlier.
Since a complex trap remains active over the course of several rounds, it might be possible to predict its future behavior by examining how it functions. This information can give its targets a much better chance of thwarting it. To minimize this possibility, design your trap so that it presents multiple threats that can change each round. The changes can include how a trap targets creatures (different attacks or saving throws), the damage or effects it produces, the areas it covers, and so on. Some traps might have a random effect each round, while others follow a carefully programmed sequence of attacks.
Dynamic elements usually occur according to a schedule. For a room that floods, you can plan out how the rising water level affects the area each round. The water might be ankle deep at the end of the first round, knee deep the next, and so on. Not only does the water bring a risk of drowning, it also makes it harder to move across the area. On the other hand, the rising water level might allow characters to swim to the upper reaches of the chamber that they couldn’t get to from the floor.
Dynamic elements can also come into play in reaction to the characters’ actions. Disarming one element of the trap might make the others deadlier. Disabling a rune that triggers a fire-breathing statue might cause the statue to explode.
The advice on triggers given for simple traps also applies to complex traps, with one exception. Complex traps have multiple triggers, or are designed such that avoiding a trigger prevents intruders from reaching the area the trap guards. Other complex traps use magical triggers that activate on specific cues, such as when a door opens or someone enters an area without wearing the correct badge, amulet, or robe.
Look at your map and consider when you want the trap to spring into action. It’s best to have a complex trap trigger after the characters have committed to exploring an area. A simple trap might activate when the characters open a door. A complex trap that triggers so early leaves the characters still outside the trapped room, in a place where they could decide to close the door and move on. A simple trap aims to keep intruders out. A complex trap wants to lure them in, so that when it activates, the intruders must deal with the trap before they can escape.
The trigger for a complex trap should be as foolproof as you can make it. A complex trap represents a serious expenditure of effort and magical power. No one builds such a trap and makes it easy to avoid. Wisdom (Perception) and Intelligence (Investigation) checks might be unable to spot a trigger, especially a magical one, but they can still give hints about the trap before it triggers. Bloodstains, ashes, gouges in the floor, and other clues of that sort can serve as evidence of the trap’s presence.
A complex trap acts repeatedly, but unlike characters and monsters, traps don’t roll for initiative. As mechanical or magical devices, their active elements operate in a periodic manner. When designing a complex trap, you need to decide when and how often its active elements produce their effects.
In a trap with multiple active elements that work in concert, those different elements would act on different initiative counts. For instance, on initiative count 20, blades sweep across a treasure vault, driving the characters back into the hallway. On initiative count 10, magic darts fire from statues in the hallway while a portcullis falls to confine the characters.
Initiative 10. If a trap’s active element takes time to build up its effects, then it acts on initiative count 10. This option is good for a trap that functions alongside allied monsters or other guardians; the delay before it acts can give guards the chance to move out of its area or force characters into the area before the trap triggers.
Initiative 20. If an element is designed to surprise intruders and hit them before they can react, then it acts on initiative count 20. This option is generally best for a complex trap. Think of it as the default. Such a trap acts quickly enough to take advantage of most characters, with nimble characters like rogues, rangers, and monks having the best chance to move out of the area before the element activates.
Initiative 20 and 10. Some active elements are incredibly fast acting, laying waste to intruders in a few moments unless countered. They act on initiative count 20 and 10.
COMPLEX TRAPS AND LEGENDARY MONSTERS
A complex trap is like a legendary monster in some ways. It has several tricks it can use on its turn, and it remains a threat throughout the round, not just on its turn. The trap’s active elements are like a legendary creature’s normal actions, and its constant elements are equivalent to legendary actions — except they are tied to specific areas in the trapped room.
Although a legendary creature can move, improvise actions, and so forth, a trap is set to a specific script — an aspect that has the potential to make a complex trap stale and predictable. That’s where dynamic elements come in. They keep the players on their toes and make dealing with a complex trap feel like a challenging, evolving situation.
Defeating Complex Traps
A complex trap is never defeated with a single check. Instead, each successful check foils some part of it or degrades its performance. Each element of the trap must be overcome individually to defeat the trap as a whole.
As part of determining how your trap can be overcome, look at your map and consider where the characters must be located to attempt an action that can foil part of the trap. As a rule, the characters should need to be near or adjacent to an element to have a chance of affecting it. An element can be designed so that it protects itself. A fighter might be able to break a whirling blade, but moving close enough to attack it requires giving the blade a chance to strike.
What methods are effective against your trap? Obvious candidates are activities covered by the same sorts of checks used to defeat simple traps, but use your knowledge of the trap’s design to identify other options. A valve that leaks poison gas into a room can be stopped up. A statue that emits a deadly aura can be pushed over and smashed. Attacks, spells, and special abilities can all play a role in undermining a trap.
Leave room for improvisation by the characters. Don’t create a few predetermined solutions and wait for the players to figure out the right approach. If you understand the mechanism behind how a trap works, that makes it much easier for you to respond to the players’ ideas. If a character wants to try something you haven’t allowed for, pick an ability, assess the chance of success, and ask for a roll.
Shutting down one part of a complex trap usually requires multiple successes. As a default, it takes three successful checks or actions to disable an element. The first successful check might reduce the element’s saving throw DC or attack bonus. The second successful check might halve the element’s damage, and the final successful check shuts it down.
For elements that don’t attack, allow each successful check to reduce that element’s effectiveness by one-third. A lock’s DC is decreased, or a gate opens wide enough to allow a Small character to squeeze through it. A mechanism pumping poison gas into the room becomes defective, causing the gas’s damage to increase more slowly or not at all.
It takes time to disable a complex trap. Three characters can’t make checks in rapid succession to disarm a complex trap in a matter of seconds. Each would get in another character’s way and disrupt the effort. Once a character succeeds on a check, another character can’t attempt the same check against the same trap element until the end of the successful character’s next turn.
Not all of the characters’ options need to be focused on stopping a trap from operating. Think of what characters can do to mitigate or avoid a trap’s effects. Making the trap vulnerable to this sort of effort is a way to engage characters who might be ill-suited to confront the trap directly. A successful Intelligence (Religion) check might provide insight into the imagery displayed by a trap in a temple or shrine, giving other characters a clue about how and where to direct their efforts. A character could stand in front of a dart trap while holding a shield that the darts can target harmlessly, while other characters trigger that element as they work to disable it.